1. Field of the Invention
The present invention is related to a rotor assembly capable of dissipating heat and particularly to a rotor assembly, which is capable of removing heat from the rotor of a motor.
2. Brief Description of the Related Art
Referring to FIG. 1, the rotor device in a conventional fan includes a fan frame 11 and a hub 12. The fan frame 11 provides a support base 111 with a hollow axial barrel 112 and a bearing 113 is received in the axial barrel 112. A stator 13 fits with the outer surface of the axial barrel 112 such that the stator 13 can be located at the support base 111. The hub 12 has a closed end and an open end with an annular cover 14 inside. The annular cover 14 has a projection part 141 corresponding to the closed end of the hub 12 and a rotor 15 is attached to the inner lateral side of the annular cover 14. A plurality of radial fan blades 121 are formed at the outer side of the hub 12. A shaft 16 is attached to the hub 12 at an end thereof and passes through the bearing 113 at another end thereof such that the hub 12 and the annular cover 14 can movably connect with the support base 111.
However, there is a problem occurring during the preceding rotor device running. Once the stator 13 and the rotor 15 are magnetized to rotate the hub 12 and the annular cover 14 due to phase changing, the fan blades 121 are driven to move fluid for cooling heat generation parts. But, heat generated from rotation of the rotor 15 relative to the stator 13 is enclosed by the hub 12 such that most of the heat stays in the hub 12 because of low heat exchange with the outside air. As a result, not only life span of the motor is shortened but also heat in the system increases.
Further, U.S. Patent Publication No. 2004/0075356 discloses a fan rotor, which includes a hub with a closed wall and an inner wall and a metal ring attached to the inner wall and disposed in the pipe shaped hub. A magnetic ring is provided in the metal ring. The hub has a plurality of locating parts to allow the metal ring being supported in the hub.
However, the fluid in the hub moves vertically while the hub rotates and flow path of the fluid are not in accordance with the through holes provided at the hub such that it is hard for the internal fluid moving outward via the through holes, i.e., the convection efficiency is low. Further, the hub is made of plastics, which is low heat conductivity, and unable to assist natural convection between the heat inside the hub and the outside air. Under this condition, undesirable cooling is obtained and the entire heat dissipation is ineffective.